Heretofore, in the film forming devices, such as a PVD device, a CVD device, an ion plating device, and a vapor deposition device, exposure devices, and etching devices, a subject to be processed, such as a silicon wafer, has been forcibly adsorbed to an evenly and smoothly finished surface of a plate-like object in order to fix the subject to be processed with good accuracy. As an adsorption means, an electrostatic chuck utilizing electrostatic adsorption force has been used.
In the electrostatic chuck for use in these film forming devices and etching devices, one principal surface (one largest surface) of a plate-like ceramic base body containing ceramics serves as a placement surface (adsorption surface) and an adsorption electrode is provided inside of or on the other principal surface (the other largest surface) of the ceramic base body, for example. Thus, a subject to be processed can be forcibly adsorbed to the placement surface and fixed by applying a DC voltage to the adsorption electrode to develop electrostatic adsorption force, such as Coulomb force generated by dielectric polarization and Johnson-Rahbek force generated by a slight leakage current, between the adsorption electrode and the subject to be processed.
In the electrostatic chuck, a lift pin for removing the subject to be processed from the placement surface is provided in such a manner that the lift pin can be desirably projected from a circumferential portion of the placement surface, the portion corresponding to a circumferential portion of the subject to be processed.
It is known that in an existing electrostatic chuck for use in plasma treatment, so-called residual adsorption occurs in which the adsorption force remains even after the DC voltage application to the adsorption electrode is canceled. The residual adsorption results from the fact that when electrons are injected from plasma into the subject to be processed, fixed charges (holes) are generated in the ceramic base body, and then the fixed charges (holes) remain in the ceramic base body even after the DC voltage application is canceled.
Herein, there has been a problem in that when it is attempted to remove the subject to be processed from the placement surface with the lift pin in the state where the residual adsorption force is high, the subject to be processed is deformed or broken.
Then, a method is proposed in which a charging control electrode that contacts with an adsorbed wafer is provided on a placement surface of an electrostatic chuck and the charging control electrode is operated as a ground electrode when releasing the adsorption (refer to PTL 1). By the use of such a fixed charge removing method, deformation or breakage of a subject to be processed can be suppressed.